You asked for suggestion for a long story, so here it's one.
It's based on bigamy plot. Everything upto Ranbir and Rhea honeymoon; that was foiled by Prachi, should be same as that in show. Next up was Vikram and Pallavi's anniversary function.
In the show we see that PRANBIR make up during that party and unofficially reunite (until that horrible Mahashivratri night plot of Rhea pretending to have slept with Ranbir)
But in your story, show them at odds with each other in Vikram Pallavi's anniversary party too. Show that Prachi and Siddharth were quietly working in the background to expose Rhea and Alia, to prove that those plotted the entire scene of Prachi and Siddharth found on one bed by Ranbir.
Prachi and Siddharth should prove in front of all the guests that Rhea and Alia planned the character assassination of Prachi and Siddharth.
This should send Ranbir in overwhelming guilt and grief and he should grovel on his knees in front of Prachi; but Prachi should pack her bags and leave Kohli mansion, stating that the objective she'd come there: to prove her innocence and expose the culprits has been accomplished and she doesn't have anything to stay for.
And next you should show how Ranbir redeems himself and wins Prachi's forgiveness.
This would be one of the best stories, if executed properly.
